For many years, alkanolamides, and particularly diethanolamides derived from lauric, stearic or coconut oil fatty acids, have been commonly and primarily employed as cost-effective foam boosters, foam stabilizers, and viscosity builders in liquid surfactant formulations where good foam generation is needed and desired. For example, foaming properties are particularly desirable and important in personal care cleanser products, such as shampoos, body cleansers; bubble baths and the like, and light duty household cleanser products, such as liquid dish washing products, liquid hand soaps and the like.
Cocodiethanolamides, in particular, have, for many years, been important nonionic surfactants in the industry and are commonly referred to as cocamide DEA, the name assigned this material in the International Cosmetic Ingredient Dictionary, Sixth Edition, published by The Cosmetic, Toiletry, and Fragrance Association (1995) (hereafter “INCI Dictionary”), the disclosures of which are incorporated herein by reference. Such name assignments are conventionally referred to as INCI names and will be so used herein.
Cocamide DEA derivatives are commercially available in pourable, pumpable, liquid form at ambient room temperature (about 30° C.), which form is particularly desirable, easy to handle and, in trade parlance, cold-mixable, i.e., desirably mixed into liquid formulations at ambient room temperature without requiring heating. Cold mixing is industrially desirable as it avoids heating the compounded formulation, thereby avoiding deteriorating heat-sensitive ingredients when present, minimizing the possibility of heat-induced product instability, reducing loss of volatiles, including water, lowering energy costs and manufacturing costs and the like.
Recently, however, the diethanolamines, which are used to manufacture diethanolamide derivatives, became the subject of certain animal toxicity studies which were reported to the public in the popular press. The negative press and toxicity issues raised by the publication of this report, in turn, created, in the minds of the public, a perceived toxicity associated with the presence of diethanolamides and of cocamide DEA, in particular, which appeared commonly as a listed ingredient on the labels of most personal care cleanser products. Consequently, this negative public opinion has created a need and desire in the personal care industry to replace diethanolamides with alternate foam boosters and foam stabilizers that are still functional, are substantially free of diethanonolamine or diethanolamides, and preferably are cold mixable at ambient room temperature.
It is known that monoalkanolamides, derived from the reaction of C2—C6 alkanolamines, such as monoethanolamine, isopropanolamine, diethylene glycolamine (2-(2-aminoethoxy)ethanol) and the like, and fatty acids having from about 8 to about 24 carbon atoms are potentially functional in applications requiring foam boosting, foam stabilizing and viscosity building. In particular, coconut oil derived monoethanolamine derivatives are of great commercial interest for use in personal care and household products.
Coconut monoethanolamide, referred to hereafter by the INCI name cocamide MEA, is known to have more foam boosting efficacy and more viscosity building efficacy than cocamide DEA. However, unlike cocamide DEA, cocamide MEA, is not commercially available as a pourable, pumpable, liquid form at ambient room temperature. The existing cocamide MEA products of commerce are normally substantially solid products sold in flaked form. Moreover, cocamide MEA is insoluble in water, so to incorporate it into an aqueous surfactant formulation, the compounded formulation must be heated above the melting point of cocamide MEA (above 60° C.). Additionally, cocamide MEA in heated molten form, as well as in unheated flaked form, is susceptible to browning discoloration on exposure to air during storage over a period of time. Such solubility and discoloration problems have limited the use of cocamide MEA, particularly in personal care products.
Monoalkanolamide derivatives prepared from the reaction of either monoethanolamine or isopropanolamine and vegetable oil unsaturated fatty acids, such as from soybean or canola (genetically modified rapeseed oil), have a lower melting point than that of coconut oil fatty acid derivatives, but also are not obtained in liquid form at ambient room temperature. These vegetable oil derived monoalkanolamides can be converted to a form remaining liquid at ambient room temperature with further chemical modification, such as alkoxylation with ethylene oxide, propoxylation with propylene oxide or a combination thereof. However, while such chemical modification can reduce the cloud point of the original starting monoalkanolamide, it normally produces an undesirable discolored product that is less effective than the unmodified monoalkanolamide in foam stabilizing or viscosity building properties. Further, the use of ethylene oxide is often looked upon as a “non-natural” feedstock, particularly from an environmental and aesthetic viewpoint, and can introduce other potentially toxic impurities, such as dioxane. Additionally, extra chemical processing increases handling and manufacturing costs.
It is known that soybean monoalkanolamide and canola monoalkanolamide derivatives prepared with diethylene glycolamine are in liquid form at ambient room temperature. However, such soybean and canola oil derived diglycolamides have undesirable brown colorations, undesirable strong odors and when used for viscosity control applications, produce an undesirable “stringy” viscosity, making them aesthetically and functionally unsuitable for personal care products. Additionally, the browning coloration of these monoalkanolamides in an air atmosphere typically worsens in appearance over time to a much greater extent than that normally observed in cocamide MEA.
Prior attempts to incorporate monoalkanolamides in surfactant formulations without heating the surfactant formulations have been made by employing solvents, such as cosmetically acceptable alcohols, for example, ethanol, isopropanol, and the like, or polyols, such as propylene glycol, glycerin and the like, or employing a hydrotroping agent, such as sodium xylene sulfonate. However, the use of solvents, particularly volatile alcohols, raises environmental issues and increases handling and manufacturing costs.
Thus, there is an ongoing, unresolved, commercial need for a relatively concentrated, high solids form of liquid monoalkanolamide delivery system, particularly for monoethanolamide, that can be cold mixed into separately prepared aqueous surfactant containing formulations, and cleanser formulations in particular, which typically contain a principal surfactant for the purpose of detersiveness and foaming. The novel cold mixable, liquid monoalkanolamide surfactant emulsions of this invention provide such a delivery system.